section 9: cutter radius compensation · 204 section 9: cutter radius compensation april 2003 fadal...

Fadal User Manual

Section 9: Cutter Radius Compensation

Cutter Radius Compensation

Cutter Radius Compensation (CRC) is used in a program to allow the operatorto alter the path of a cutter.

EXAMPLE: After cutting the part with path 1, the operator measured the part anddetermined that the part was undersized. By increasing the amount of thediameter in the tool table and running the program again with another part inthe fixture, path 2 cut the part to the correct dimension.

Format 1 The H word in the program will pick up the tool length offset (TLO) and the tooldiameter offset. It should be used before using the G41 or G42 codes. The Dword can be used to pick up a new diameter, however, it is not necessary inFormat 1. If a D word is used, it should appear in the program after the H word.Whatever diameter is picked up by the H word is then overwritten by the Dword. It can be used on the same line as the G41 or G42 codes.

M6 T1G0 G90 S7500 M3 X-2. Y-1.H1 M7 Z.1 The H will pick up the TLO and the diameter from the tool table

Format 2 The H word in the program will only pick up the tool length offset (TLO). Itshould be used before using the G41 or G42 codes.

UNDERSIZED PART OUTLINE

GOOD PART OUTLINE

PFAD 1

PFAD 2

Figure 9-1 Cutter Radius Compensation

April 2003 Section 9: Cutter Radius Compensation 203

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The D word must be used to pick up the tool diameter. It can be used on thesame line as the G41 or G42 codes or on any line before the G41 or G42 codes.

M6 T3G0 G90 S800 M3 X3.641 Y-2.224H3 D3 M8 Z.1 The H and the D words are used to pick up the TLO and the tool diameter

G40 - Cancel Cutter Radius Compensation

See G42.

G41 - Climb Cut (cutter left)

See G42.

G42 - Conventional Cut (cutter right)

The G40, G41, or the G42 can be used before or after other codes in a line,without changing what happens. G41 X1. G1 F35. and G1 X1. F35. G41 wouldboth function the same way.

G41: OFFSET THE CUTTER TO THE LEFTOF THE PROGRAMMED PATH

G42: OFFSET THE CUTTER TO THE RIGHT OF THE PROGRAMMED PATH

Figure 9-2 Conventional Cut

204 Section 9: Cutter Radius Compensation April 2003

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Climb and Conventional Cutting

Climb cut the inside of a part by following a general counterclockwise path.Climb cut the outside of a part by following a general clockwise path.

Conventional cut the inside of a part by following a general clockwise path.Conventional cut the outside of a part by following a general counter clockwisepath.

G41

G41

G41: CLIMB CUT THE PROGRAMMEDPATH

Figure 9-3 Climb Cutting

G42

G42

G42: CONVENTIONAL CUT THEPROGRAMMED PATH

Figure 9-4 Conventional Cutting


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The H and the D Word with CRC

H and D Word Use Cutter Radius Compensation must be called with offset call. In Format 1 mode,the offset number is selected by the use of an H word. In Format 2, the D wordis used. The amount applied will be 1/2 the diameter specified in the table.Positive or negative diameters are allowed. A negative diameter will cause thedisplacement in the opposite direction. In Format 2 mode, the cutter offsetspecification in the tool data table may be changed to register diameter orradius

(see Section 8, SETP). The D word in the program (Format 2) indicated whichoffset to use. In Format 1, the use of the D word will override any diameteroffset selected by the last H word. The next H word will override the previous Dword.

The use of the H99 with the Q word, in Format 1, may be used to specify aspecific tool diameter. This diameter value given to the Q word is placed intothe tool table location 99. This new value will be used until a new H word or Dword is specified.

EXAMPLE: M6 T1 (.506 E.M.G0G90S200 M3 E1 X0Y0H1 Z.1G1 Z-1.G41X3.Y2.H99 Q.5 This specified a tool diameter of .5To reverse direction of cut the G41 or G42 mode can be switched without canceling the other code. This can be used when kellering (cutting in both direction to remove material).

Advantages of Climb Cutting

When using climb cuts, the cutter will bend away from the wall being cut. Thiswill automatically leave stock on the wall. Because it will leave stock, this willeliminate the need to program a different roughing pass around the partoutline. A roughing pass and a finish pass will result from using the same pathtwo times around the outline. After material has been removed on the firstpass, tool pressure is reduced and the tool will not bend on the second pass.Sometimes more than two passes are required depending on the length andtype of cutter and on the type of material being cut. For a second pass use thecopy command to copy the program, or use subroutines or subprograms.


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Simply increasing the diameter of the tool in the tool table will not always workfor a roughing pass. Inside radii could be a limiting factor. If the tool diameter isincreased to a size larger than an inside radius on the part outline, a “TOOLDIAMETER TOO LARGE” message will appear.

Note: The tool is bending the first time around, so program the tool to be .005to .015 above any floors (the longer the tool the more it will bend). On thesecond or final pass, program the tool to cut the floor. The second passmay also use a different feedrate and spindle RPM.

Note: Because of the rigidity of a bed style vertical machining center, it is notnecessary to program a conventional cut around the part outline and thenfinish the part with a climb cut. Although this is true for most materials,plastics and hardened materials are the exception.

In most cases climb cutting will allow the tool to last longer. It is notrecommended to use climb cutting through a hardened surface, as in awelded, flame hardened, flame cut, hard anodized, or a hot rolled surface.

Climb cutting allows a higher RPM to be used, and along with a higher RPM,higher feed rates (as compared to conventional cutting).

The heat created at the tool and work piece is less with a climb cut than with aconventional cut. With tools as short as possible and a high RPM, the chips willtake the heat away from the tool and the work piece.

Note: When using a higher RPM, use cutters with good chip clearance. Usetwo or three fluted end mills in place of cutters with four or more flutes.

Advantages ofConventional Cutting

Use conventional cutting to “scoop out” or cut through hardened material. Ifthe cutter is deep enough to start the chip in soft material, the chip will

.005/.015

FINISHED FLOOR

Figure 9-5


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continue to form up through the hard material. This will break down the cutter,but it will last longer than using a climb cut.

The heat between the cutter and the work piece is greater with a conventionalcut, so a this cut is used for a finish cut for some plastics. It will leave asmoother finish than a climb cut.

In some cases a conventional cut is used to push a flimsy part up against afixture. If a climb cut was used, the part would not have any support and wouldbend because of the cutting action.

WARNING: Climb cutting causes the cutter to bend away from the wallbeing cut, and conventional cutting will cause the cutter to bend into thewall being cut.

Guidelines for Using CRC

Use CRC (G41, G42) only when cutting a part outline (part path program).Program motion of the center of the tool when cutting areas other than walls,using G40 (CRC cancel). When programming the motion of the center of thecutter (tool path program) using G40, the control will not alter the path.

CRC (G41, G42) should only be used when cutting a part outline. Program theoutline of the part (using the print dimensions). The control will compensate for

!

G41

G40

(CRC IS USED)PART PATH PROGRAM

(CRC NOT USED)TOOL PATH PROGRAM

Figure 9-6 Using CRC


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the radius of the cutter being used and cut to leave the programmed partoutline.

Note: Cutter Radius Compensation must be canceled prior to locating thecenter line of the tool to a specific point.

General Rules

1) G90 X-.4 Y.4 Position the tool, at least the tool radius away from the wallto be cut

2) Y0 G41 G1 F10. With the move to the wall, use G41 to apply CRC

3) X3.01 Move along the wall

4) Y.4 G0 G40 With the move away from the wall being cut, use a G40 tocancel comp

TO CLEAN OUT THE POCKETPROGRAM THE MOVEMENT OF THE CENTER(TOOL PATH PROGRAM)

NUR CRC BENUTZEN UM DIE WÄNDE(PART PATH PROGRAM)

Figure 9-7

+

2

G41

1 4

G40

3

+

Figure 9-8 General Rules


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Note: The distance of the move up to the wall and away from the wall must begreater than or equal to the radius of the cutter.

Examples ofApplying and

Canceling CRC

These examples represent part outlines and are intended to give general ideason applying and canceling cutter radius compensation.

1) Position the tool, at least the tool radius away from the boss.

2) Apply CRC along with the move up to the boss.

3) Program the circular move.

4) Cancel CRC along with the move back to the first position.

1) Position the tool, at least the tool radius away from the line from 2 to 3.

2) Apply CRC along with the move from position 1 to 2.

3) Complete the entire path.

2

G40

G41

1 .

Figure 9-9 Applying & Canceling CRC (1)

3 4

6

2

5

1

G40

G41

.



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4) Cancel CRC along with the move from position 5 to 6.

1) The radius of the lead in lead out radius must be larger than the radius ofthe tool to be used.


3) Complete moving around the path.


1) Apply CRC with the move from position 1 to 2. Position 1 must be at leastthe radius of the tool to be used away from the edge of the circle to be cut.Position 1 does not need be at the center of the circle.

2) Cut counter clockwise around the circle.

3) Cancel CRC along with the move away from the circle from position 3 to 4.

. 1

5

4

2

63


3

G412

G404

1



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1) The radius of the lead in lead out radius must be larger than the radius ofthe tool to be used.


3) Complete moving around the path.


2

43

5

6 1


10

2

9

1

11

12

34

G40 G41

5

6

7

8



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1) Apply CRC along with the move up to the part wall (from position 1 to 2).

2) Move around the part.

3) Cancel CRC along with the move away from the part (from position 11 to12).

1) Apply CRC along with the move up to the part wall. This move must be atleast the radius of the tool to be used away from the part.

2) Move in a general clockwise direction around the outside of the part (forclimb cut).

3) Cancel CRC along with the move away from the part. Again, this move mustbe at least the radius of the tool to be used away from the part.

1) Apply CRC along with a move up to an extended wall from the part. Thismove must be at least the radius of the tool to be used away from the part.

G41

G40


G40

G41



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2) Move in a general clockwise direction around the outside of the part (forclimb cut) to an extended line off the wall of the part.

3) Cancel CRC along with the move away from the extended line. Again, thismove must be at least the radius of the tool to be used away from theextended line.

O-Ring Groove Example

In an O-ring groove, consider both circles of the groove as separate walls.

1) Start at the midpoint between the walls.

2) Apply CRC (comp) moving to the first circle.

3) Cut the circle.

4) Cancel comp moving back to the midpoint.

Following the general rule, always cancel CRC when leaving a wall. When goingfrom one wall to the other, cancel comp moving to the midpoint, then applycomp again moving to the other wall.

5) Apply comp moving to the second circle.

6) Cut the circle.

Figure 9-17 O-Ring Groove


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7) Cancel comp moving back to the midpoint.

Perpendicular Rule

It is best to apply and cancel comp using moves perpendicular to the wall.When perpendicular moves are used, the cutter will follow the programmedmove. Otherwise, the cutter will not follow the move to or away from the wall.

Moving perpendicular to and from a wall is best. When comp is on, the tool willremain perpendicular (tangent) to the wall it is touching. Beginning and endingthe move perpendicular will keep the tool perpendicular for the entireprogrammed path.

Comp can be applied with a move that is not perpendicular; however, theactual move the tool will make when it is moving up to and away from the wallcannot be predicted. Even though it is possible to turn comp on, with a movethat is not perpendicular the wall, this method is not recommended.

Any line, at any angle, that extends through the center of a circle is consideredperpendicular to the circle. When starting comp such a line is recommendedfor contoured walls.

Figure 9-18 Perpendicular Rule


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Fillet Radii and Step Downs

All features on a print have tolerances. Inside corner radii (“fillet” or “blend”radii) usually have more tolerance than other features. Take advantage of thisand program inside corner radii larger than the radius of the tool to be used forcutting the part. Also remember, when a larger tool diameter is going to beused for a roughing pass, program fillet radii larger than the intended toolradius. In the drawing above, the tool radius in the tool table is too large for theprogrammed fillet radius. In the drawing below, the programmed fillet radius islarger than the tool radius in the tool table. The operator can increase the toolradius in the table up to the smallest inside fillet radius.

In the drawing above, the step down distance is smaller than the radius of thetool. The cutter will not be able to step down, and a TOOL DIAMETER TOOLARGE message will appear. The picture below shows how to program a filletradius from the corner of the step and tangent to the bottom wall. Again makethe fillet radius large enough to accept a radius for a roughing pass.

Note: It is always better to program a fillet radius between two intersectingfeatures, rather than to leave them as steps and intersections.

Figure 9-19 Fillet Radii and Step Downs

Figure 9-20 Fillet Radius Larger than Tool Radius


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Program Example

The print above shows the inside radii as .375 in four places. A .75 end millcould be used to form the inside radii; however, if the end mill is used to formthe inside radii, the cutter will bend into the corners and chatter. Byprogramming an inside corner radius larger than the radius of the tool to beused, the problem of bending into the corner and chattering will be eliminated.Drilling out the corners, slowing down, speeding up or dwelling in the cornerswill not work!

Sometimes the tolerances do not allow the programmer to program an insidecorner radius larger than a common sized end mill. For example, a print mayallow the corner to be no larger than .250. Using a .5 end mill would cause thecutter to form the inside radius. When forming an inside radius with the radiusof the cutter is not desirable, use a .375 cutter or reground .5 end mill andcontour the .250 fillet radius.

Note: Never use a cutter to form an inside corner radius and expect goodresults on the part!

Note: Always contour an inside corner radius!

EXAMPLE: N1 O1 (CRC RECTANGULAR WINDOW EXAMPLEN2 L100 (POCKETN3 Y-1.12N4 X.875 Y-1.5 I.375 J0 G3N5 X1.625N6 X2. Y-1.125 I0 J.375N7 Y-.875N8 X1.625 Y-.5 I-.375 J0N9 X.875


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N10 X.5 Y-.875 I0 J-.375N11 M17N12 M30N13 (TOOL #1, 3/4 2FL EM (CRC)N14 G0 G90 S5000 M3 E1 X.875 Y-.875N15 H1 D1 M7 Z.1N16 G1 Z-.4 F10. G8N17 X.5 G41N18 F35.N19 L101N20 F45.N21 L101N22 X.875 G40N23 M5 M9N24 G0 H0 G90 Z0N25 M6 T2

The subroutine includes only the moves around the wall of the window.Programming in this manner allows the subroutine to be called up two times fortwo passes around the wall. The move up to the wall at N17 turns comp on,and is using the feedrate from N16. A new feed at N18 is programmed andthen the sub is called one time at N19. A feedrate change is made at N20, thenthe sub is called again at line N21. When running this program, the moves willlook as if they are continuous from the first time around to the second timearound. This is because all of these moves are preprocessed. The move awayfrom the wall, while turning comp off, is made at line N22.

Corner Rounding When cutter radius compensation is applied, it can use two different methodsto move around a corner: rolling and intersectional.

Figure 9-21 Corner Rounding


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M96 Cancel Intersectional CRC (Rolling)

M97 Intersectional CRC

The M96 or M97, as default codes, can be selected when using the SETPcommand.

The M96 mode of CRC is more commonly used. In most cases it is also thesafer mode. Using this mode insures that the tool will always be touching theprogrammed walls. An M97 allows the tool to move away from theprogrammed walls, where it might gouge some other programmed feature.These two codes are named by the way they move around any corner:tangentially for M96 and intersectionally for M97.

When to use M96 and M97

Each code produces a different type of corner on the floor; however, both willcut a mitered corner on all top edges.

Figure 9-22 Rolling

Figure 9-23 Using M96 and M97


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M96 produces a rounded corner on the floor. M97 produces a mitered corneron the floor.

Note: Some prints will specify the type of corner needed on the part. In mostcases the type of rounding used will only affect the part visually, notfunctionally.

M96 and M97 are default codes, and can be established by using the SETPcommand. M96 is more commonly used as default because M97 causes thetool to bypass a corner which may cause the tool to bump into another portionof the part.

If a part has steps, and blend radii were not used to move up and down thesteps, use M97. The control will accept the program better than in the M96mode. As mentioned earlier in regards to fillet radii and step downs, it is betterto always program a fillet radius between two intersecting features, rather thanto leave these features as steps and intersections. If fillet radii areprogrammed, use the M96 mode.

Grooves, slots, and O-ring grooves should use M96. This is most importantwhen the diameter of the tool is almost equal to the width of the slot or groove.

CRC & Z Axis Moves While CRC is in effect, a Z move can be made to move to a new Z level or toexecute a helical move. The control will “look ahead” of Z moves andcompensate the cutter for the next X or Y move.

Figure 9-24 Rounded/Mitered Corners


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M6 T1 (TOOL #1, 1/2 DIA. FINISH EM (CRC)G0 G90 S6000 M3 E1 X24.5 Y.3H1 M7 Z-.5X24.2 G41Y-1.02 G1 F35.Z-.2 Here is a move to a new Z level with CRC still in effectY-1.9 G5Y-2.02X24.5 G0 G40

Applying Compensation with a Z Move

CRC can be applied along with a Z move. When comp is applied with a Z move,the cutter will offset tangent to the next X or Y axis move. The next line for thecontrol to move tangent to can be a linear move or a circular move.

Note: Format 1 and Format 2 apply the offset differently.

EXAMPLE: Format 1

A G41/G42 in the same line with a Z move will offset the cutter before making aZ minus move and after a Z plus move.

M6 T1 (TOOL #1, 3/4 DIA. EM (CRC)G0 G90 S1500 M3 E1 X.6 Y-4.6H1 Z.1 M7Z-.52 G41 Here the cutter offsets first, then the Z move is madeX0 Y-3.7 G1 F15.Y.02Z.1 G0 G40 Here the Z move is made first, then comp is canceled

Note: The example program above will operate differently in Format 2. See thenext example program for Format 2.

EXAMPLE: Format 2

In Format 2 the Z move and the offset move will be made together.

M6 T1 (TOOL #1, 3/4 DIA. EM (CRC)G0 G90 S1500 M3 E1 X.6 Y-4.6H1 Z.1 M7Z-.52 G41 Here the offset and Z axis move at the same timeX0 Y-3.7 G1 F15.Y.02


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Z.1 G0 G40 Here the Z axis moves and the offset is canceled at the same time

EXAMPLE: Format 1 & 2

The sample program below will operate in the same way for Format 1 andFormat 2.

M6 T1 (TOOL #1, 3/4 DIA. EM (CRC)G0 G90 S1500 M3 E1 X.6 Y-4.6H1 Z.1 M7G41 Here the cutter offsetsZ-.52 Then the Z move is madeX0 Y-3.7 G1 F15.Y.02Z.1 G0 Here the Z move is madeG40 Then comp is canceled


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Applying Compensation with a Z Move on a Circle



M6 T1 (TOOL #1, 3/4 DIA. EM (CRC)G0 G90 S1500 M3 E1 X2.4 Y-1.2H1 Z.1 M7G41 Here the cutter offsets perpendicular to the circleZ-.52 Then the Z move is madeX-1. Y-1.1225 I-1.4 J-4.8 G3 Here the circle cut is madeZ.1 G0 Here the Z move is madeG40 Then comp is canceled

Figure 9-25 Cutter Offset


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CompensationExample



M6 T1 (TOOL #1, 1/2 DIA. EM (CRC)G0 G90 S5000 M3 E1 X.332 Y-2.2 This moves to point oneH1 Z.1 M7G41 Comp is applied perpendicular to the next moveZ-.27 Z moves downX0 Y-1.625 G1 F30.Y-.25X.25 Y0 I.25 G3Y.3 G40 G0 Comp is canceled along with the move away from the wall being cutZ.1X1.75 This moves to point sixZ-.27Y0 G41 Comp is applied with the move up to the wall to be cutX2. Y-.25 J-.25 G3Y-1.625X1.668 Y-2.2Z.1 G0 Z moves up perpendicular to position tenG40 Comp is canceled and positions over point ten

Figure 9-26 Compensation Example


section 9: cutter radius compensation · 204 section 9: cutter radius compensation april 2003 fadal...

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